1. Field of the Invention
This invention relates to a guide shaft structure adopted to guide a cross arm in a pushbutton tuner.
2. Description of the Prior Art
As conventionally known, a pushbutton tuner used in a radio receiver, etc. is so arranged as to select one of a plurality of tuning coils when a tuning button is pushed and determine the stroke of the tuning coil inserted in the associated core, thus to select only a special broadcasting station. In order to slidably mount the pushbutton with respect to the tuner body so as to permit such a tuning operation, an upper plate 1 mounted on the tuner body is formed with guide slits 2 in each of which a guide pin 4 and a guide shaft 5 provided on a cross arm 3 are inserted to allow the cross arm 3 to slide along the guide slit 2 as shown in FIG. 1 to FIG. 3(A).
The guide pin 4 comprises a caulked portion 4a for being caulked on the cross arm 3, an inserted portion 4b to be inserted in the guide slit 2 and a flange portion 4c formed at the top end thereof for being in slidable contact with the upper surface of the upper plate 1 to regulate the downward movement of the cross arm 3. On the other hand, the guide shaft 5 comprises a caulked portion 5a for being caulked on the cross arm 3 and a guide portion 5b for being inserted in the guide slit 2 and regulating horizontal movement of the cross arm 3 with respect to the upper plate 1.
In order to precisely guide the cross arm 3 in such guide mechanism it is necessary to increase sizewise accuracy of the guide portion 5b of the guide shaft 5. The accuracy is sometimes required to an extent of 1/100 mm so that even a small deformation on the outer periphery of the guide shaft 5 is not allowable.
However, since the guide shaft 5 is to be caulked on the cross arm 3, a conventional guide shaft has had such a drawback to be apt to deform at the upper corner portion and the outer periphery thereof as shown in FIG. 3(B) due to the pressure applied thereto during caulking. Such problem has not been a mere question for a guide shaft for guiding a cross arm in a pushbutton turner but such deformation at a corner portion and an outer periphery of any other guide shaft has not been avoided, either when the guide shaft is secured on another member by means of caulking.